It is well known that numerous manufacturing processes must be conducted to in precisely controlled atmospheres. For instance, a portion of the manufacturing process for electronic semiconductor devices is carried out in ovens in which the atmosphere must contain very low levels of oxygen. Some such processes require oxygen levels in the single digit part per million range. When the oven is first placed in operation, the oxygen level therein is that of the earths atmosphere, i.e. approximately 21%. If current available is oxygen sensors capable of measuring parts per million of oxygen in the single digit range are exposed to the typical 21% oxygen content of air, it takes them an exceeding long time to establish their sensitivity in the single digit parts per million range.
That is, the contamination of the sensor with the high level of oxygen prevents it from accurately reading within a reasonable time period single digit parts per million, even though the atmosphere in which it is located has reached the single digit parts per million level of oxygen. While this delay is well known, it has nevertheless been found unacceptable to ignore the failure of the sensor to indicate the desired very low level of oxygen, and to begin processing in the oven based only on the time period during which the oven has been purged of oxygen.
Numerous factors, such as leaks in the oven, variations in the level of oxygen contamination in the oven, and variations in the purity of the purging gas can all contribute to variations from an expected delay period for the atmosphere in the oven to reach the desired very low levels of oxygen. Thus, the considerable delay in the ability of the very low level sensor to accurately indicate the oxygen content of the atmosphere in single digit parts per million, delays the useful operation of the oven, resulting in an overall loss of production time, and therefore increased expense. Accordingly, it would be of considerable advantage to provide a system and arrangement in which a very low level oxygen sensor would more quickly become sensitive to a very low level of oxygen being reached in an atmosphere originally containing the typical 21% oxygen found in air.